Wireless transmission system



Feb. 11, 1925. 1,526,311

M. c. B ATSEL wmmass mmsmssxon SYSTEM Y 1 Filed Jan. 25, 192i WITNESSES: i INVENTOR Patented Feb. 17 1935.

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f Application filed zanuar zs, 1921. Serial 1%. 439,857. 1 1

Be t known that 1, .Max C. Bn'rsnn, a

citizen ofthe United States, and a resident of Wilkinsburg, in the county ofiAllegheny and State ofPennsylvania, have invented anew and useful Improvementin .Wireless Transmission Systems, of a which the following is a specification. M ii a it My invention relates to improvements in transmitting apparatus for Wireless telephone, and telegraph systems andwmore particularly to means for; coupling the ampli fying c1rcuitto theradiating' circuit. a

An object of my invention is to provide a system of amplifier circuits, comprisin a vacuum tube generator; and an ampli er,

thi e iati asy t a 1 Another object is toprovide a coupling between an oscillating system and a: radiating system thatwill keep the current in the ampl fying system Within safeyalu'es when the radiating system is untuned tothe frewith meansto couple the amplifier circuit to Will have the correct, impedance whenthe two systems'are tuned to the same frequency, for the desired output.

y In operating. vacuum-tube amplifiers with loose .coupling and low values of. re-

actance fin'the plate-circuit coil; it has been customary-{to insert resistance in the plate circuit of 1 the amplifier tube .or tubes to prevent the generation of; destructive currents iuthe plate .jcircuits when theradiating system is untunedito the frequencyof the oscillating; circuits ,The plate circuit hasa directacurrent. flow therein, asa result of the 1 plate battery orgenerato'r. IInflad dition. to this direct current there is'superimposed an alternating 1 current due to the oscillatin voltage impressed upon the grid of the tu e. .jBefore .the radiating, system, comprisin the antenna circuits, is tuned to thesame requency as the vacuum-tube amplifier there is but small load placed upon the plate circuit of the amplifier tube. This has frequently resulted, heretofore, in an alternating current of sufficient value to destroythe tube.

In order to take care of these heavy currents, resistance has customarily been inserted in the platecircuitof thetube and kept in circuit until the radiating system, comprising the antenna circuits, was tuned to the. oscillating frequency. The resistance has then been taken out of the plate primary of a loose-coup .t o thefamplifier tube circuit.

circuit of the amplifier tube, and the effective load of the tuned antenna circuit prevented currents: of. dangerous value from flowingfin that plate circuit. If, through hastelor negligence,- resistance was not inserted, the tube would be destroyed.

Another expedient which has been tried, but which proved to be impracticable, was to enlarge the inductancei that acts as the In the plate circuit of the amplifier tube, to a value sufficient to reducethe effective currentinthe platecircuit to a safe value. It has been found that, when the inductance was of large enough value: to accomplish this purposeiltherewas a large wattless coniponentgof e5 plate current which existed vhenthe antenna was tuned and coupled This wattless component of the plate current represented energy lost in heat andrso considerably limited .the percentage of-efiiciency of power 011t l1i;;

T e present inventiontmakes it possible to use a large inductance in the primary coil of the transformer and yet avoids the disadvantage of alar e wattless component of the plate current w en :theantenna is tuned.

.My system employs a enerator or oscillating tube and anampli er tube. The amplifier tube is-connected'to the radiating system: bymeans of .a power transformer containingxiron, steel or a similar substance or simply an air corewThe transformer used is one having small leakage flux, and hence. small" leakage reactanee. 1 This power transformer coupling between the amplifying system and .the radiating sys tem insures that, when the radiating system is out of tune with the amplifying system,

the current flowing in the amplifying sys tern will not be of excessive value; yet, when the two are coupled and tuned to the same frequency,gthe magnetizing current is but a small percenta e of the total power output ofthe ampli er. tube. This is because, when theradiatin system is detuned, practically all of .the larg primary inductance is available toimpedethe plate currentv but when it is tuned, the only inductive effect small one due to leakage.

Inthe drawings: Figure ,1 is a dia ammatic view of a system embodying a ransmitting apparatus employing my power-transmitting couofthe transformer in ,theplate circuit is the ing transformer;

pling between the amplifying system and the radiating system.

Fig. 2 is a diagrammatic view of the circuits of a vacuum-tube amplifier.

Fig. 3 is a diagram representing the flow of the plate current in a circuit such as is represented in Fig. 2. I

Fig. 4 is a diagrammatic View of a vacuum-tube amplifier in which a source of alternating current is used to change the potential of the grid.

Fig. 5 is a diagram illustrating the late current generated in the plate circuit 0 the tube shown in Fig. 4. Y

In Fig. 1, the numeral 1 designates a vacuum tube having a filament element 2, a grid element 3 and a plate element 4. The filament element 2is heated by means of a suitable battery 5, and a source of direct current 6, shunted by a condenser 6, supplies direct-current to the plate circuit of the vacuum tube through a choke coil 7.

The tube 1 is a generator tube and oscillates with a frequency determined by the values of capacitance and inductance in the oscillating circuit comprising a variable inductance 8 and capacitancesQand 10. Conpled to the oscillating circuit, comprising the variable inductance 8 and capacitances 9 and 10, through a condenserll, is the grid 3 of the generator tube 1. A grid-leak resistance 12 performs the usual function of grid-leak resistances in generator tubes.

An amplifier tube 13, having a filament element 14, a grid element 15 and a plate element 16, is shown with its late circuit supplied by the same source 0 direct-current 6 that supplies the plate circuit of the generator tube 1. The grid 15 of thetube 13 is coupled, through a condenser 17, to the oscillating circuit'comprising-t-he variable i-nductance8 and capacitances ,9 and 10. A suitable grid-leak resistance 18 is in circuit between the filament 14 and the grid 15. The battery 5 supplies current for heating the filament 14 which is connected in parallel with the filament 2. Any number of tubes maybe connected in parallel, as amplifiers, to obtain large power output. 7

In the plate circuit of the amplifier tube 13, is located an inductance 20, forming the primary of a transformer 21 to couple the amplifying system to the radiating system. The secondary of the transformer 21 comprises an inductance 22 whichis closely coupled to the inductance 20 which forms the rimary of the transformer. The two windings are either wound on a suitable iron or steel core as illustrated at 23,0r they may be interleaved or constructed in a special manner (lnot shown) to produce an exceptionally c ose coupling or small leakage flux. The inductance 22 lies in the radiating circuit comprising an antenna 24, a variable inductance 25 and the inductance 22 above mentioned to ground. When I speak of an iron core 23, it is to be expressly understood that I mean any of the special irons, steels or other metals used in power-transformer construction.

In Fig. 2 is shown an electron tube in which a filament element 30 is heated by an A battery 31, and the plate-filament circuit, comprising the filament 30 and a plate 32, is supplied with a B battery 33. Applying a constant negative potential to a grid 34, is a C battery 35 the negative terminal of which is connected to the grid.

Fig. 3 shows the type of current flowing in the plate-filament circuit." In the diagram shown in Fig. 3, current is the ordinate and time the abscissa. There is a constant value of plate current, as denoted by the straight line I,,. I

In Fig. 4 is shown an electron tube like that shown in Fig. 2 to which 'is added a source of alternating-current 36 to cause the value of the grid potential to fluctuate through certain limits.

Fig. 5 diagrammatically shows the'fluctuations in value of the plate current for the system illustrated in Fig. 4. Whena'source of alternating potential of sufiicient amplitude, is .placed in the grid-filament circuit, the plate current is caused to vary in accordance with the values shown in curves A, B, C and'D. The eifective value of the plate current is represented by the'dotted line I From this diagram, it isapparent that, if it were not for the high impedance of the coil 20, theefiective valuesof the plate current would be greatly increased when there is no substantial load placed upon the plate circuit of the vacuum tube and when a source of alternating potential of suflicient amplitude is inserted in the grid-filament circuit.

The effective value of plate current, under the circumstances'just described, might be great enough to destroy the vacuum .tube. Therefore, it has been customary, before the antenna circuit or radiating system was tuned to the frerpiency of the out-put oscillations of the tu e, to insert a resistance in the plate-filament circuit of sufficient value to act as an impedance to cut down the eifee tive value of the plate current to a safe limit for the tube used. This insertion of resistance was liable to be neglected, with resulting destruction of the tube.

Let us suppose that, in the case represented in Fig. 4, the primary of a transformer has been placed in the plate-filament circuit of the tube which has a relatively high primary inductance of sufficient magnitude to cut down the effective plate current to a safe value. This inductance must be high enough to take care of the effective plate current when the radiating system is not in tune with the current in the oscillating cireuit. means that the only current traversing the plate-filament circuit will be,

' the normal exciting current of the trans radiated from the antenna circuit.

But, when the radiating system is tuned to the frequency of the oscillating system and my transformer .is working under load, the

power lost in magnetizing current. is a negligible factor in proportion to the ower expended in taking care of the loadm the prisingthe varia been secondary. Hence, thelfunctioning of the transformer which I employis peculiarly suited to obtain good resultsfortwo reasons; first, when the radiating system'is not tuned to the frequency of theoscillatin system, the. plate current is held within sa e limits; 1

second, when the oscillating system and radiating system are tuned to the same frequency; in other words, when the load has put upon the plate circuit, only a negligible fraction of poweris lost because of the magnetizing current of the transformer. I l e In operation, the generator tube 1 is producin fluctuations in its plate circuit in accor ance with a given frequency re ulated by the period of thetuned circuit which includes the variable inductance 8 and the capacitances .9-land 10. Suitable conditions for sustained oscillations are present by reasonof the static coupling of the grid 3 of the generator tube 1, through the capacitance 11 to the tuned circuit combleinductance 8 and the I capacitances 9 and 10 lying within the late ductance 20 of the transformer.

the power outputof the circuit ofthe tube. The tube 13 pro ducfs i 5 the condenser 17', to the tuned circuit comprising the variable inductance 8 and the capacitances 9 and 10.

The primary 20 of the transformer 21 lies within the plate circuit of the amplifier tube 13, anc, when the radiating stem comprising the antenna 24:, the varia-b e inductance 25, and the secondary inductance 22 ofthe transformer 21, is out of tune with the frequency generated, the current in the plate-filament circuit ofthe amplifier tube 13 is held within safe values. This condition obtains lar ely by reason of the counter- 55 electromotive orce generated in the in- When the radiating system, however, is tuned to the same frequency as the oscillating system, the transformer 21 is working under load and late circuit of the tube 13 is practically all consumed in producing current in the radiating system.

By employin a power-typetransformer to couple the p ate circuitof the amplifier tube to the radiating system, I have provided an automatic check forlimiting the effective value of the plate current flowing, before the radiating system has been tuned to the V out-put frequency. Not only have I accomplished an automatic regulation of the plate current of the. amplifier tube to within safe i values, but I have done this without materially lessening the power output because theloss due to the magnetizin current of the transformer becomes negligi le when the that my invention shall be limited only by thejscope of the appended claims or the 1 showing of the prior. art.

I claim as my invention:

comprising an amplifying system, a. radiating system, and means for coupling the amplifying and radiating systems to ensure a relatively high impedance in the amplifyin system when the twolsystems are untun with respect to each other.

2. A system for transmitting oscillations comprising an amplifying system, a primary of a transformer having low leakage fiux in the amplifyingsystem, a radiating system and a secondary of the transformer in the radiating systemto' ensure a rela.- tively hi l1 impedance in the amplifying system w en the two systems are untuned with respect to each other.-

3. Asystem fortran'smitting oscillations comprising an oscillatingsystem, an amplifying system, an inductance forming the primary of atransformer in the amplifying system, a radiating system, an inductance in the radiating system forming the secondary of the transformer and means reducing a large counter-electromotive orce in the primary when the systems are untuned with respect to each other.

4. A system for transmitting oscillations comprising an oscillating system,.an amplifying system, a radiating system and an iron core power transformer coupling the two latter systems.

5. A- system for transmitting oscillations comprising an oscillating system, an amplifying system, a radiating system and means coupling the amplifying and radiating systems having a large self inductance when the two s stems are untuned with respect to each 0t er and but small power loss when they are in tune.

6. In a radio sending system, an oscillating circuit, an amplifylng circuit, a radiating circuit and a transformer of the power type having a high primary inductance in the amplifying circuit and a secondary inductance in the radiating circuit, and said transformer having a close coupling, whereby a high impedance will be present in the 1. A system for transmittingoscillations possible I primary circuit when the transformer is without load.

7. A system for transmitting oscillations comprising an oscillating system having a generator tube and an amplifier tube in which the plate circuits of the amplifier and generator tubes are conductively connected, a radiating system and a power transformer drawing exciting currents coupling the two systems.

8. A system for producing radio oscillations comprising an oscillating system having a generator tube and an amplifier tube, the plate circuits of the amplifier and gene-rator tubes being conductively connected and the grids of the tubes being statically connected to the plate circuits, a radiating system, an inductance forming the primary of a transformer in the amplifying system, an inductance forming the secondary of the transformer in the radiating system and means operatively associated with said inductances tending to produce a. relatively large counter-electromotive force in the plate circuit of the amplifier tube when the systems are untuncd with respect toeach other.

9. A system for producing radio oscillations comprising an oscillating system having'a generator tube and an amplifier tube, the plate circuits of the generator and amplifier tubes being conductively connected and the grids of the tubes statically con.- nected to the plate circuits, a radiating system and an iron core power-type transformer having a primary inductance in the oscillating circuit and a secondary inductance 1n the radiat ng circuit.

10. In combination, a power circuit carrying radio-frequenc currents, an outgoing circuit, and coupling means therebetween comprising a magnetizable member and primary and secondary energizing windings therefor, one of said windings being included in said power circuit and constituting substantially the whole of the inductance therein, the other of said windings being included in said outgoing circuit.

11. In combination, a power circuit carrying radio-frequency currents, an outgoing circuit and a coupling between said circuits including an iron core transformer having a primary winding included in said power circuit and a secondary winding included in said outgoing circuit said primary winding constituting the major part of. the inductance in the power circuit and said secondary winding constituting a minor part of the inductance in said outgoing circuit.

12. In a radio system, an oscillating circuit, a power circuit controlled thereby, an antenna. circuit and an inductive coupling between said power circuit and said antenna circuit, said coupling including an inductance in the power circuit and an inductance in the antenna circuit said inductances being closely coupled together, said antenna circuit also including means for tuning it to the frequency of the oscillating circuit and said tuning means including an inductance.

In testimony whereof, I have hereunto subscribed my name this 31st day of December 1920.

MlAX C. BATSEL. 

